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Category: Wireless

Halloween is a great time for makers, we get to make all kinds of cool costumes and spooky things. Sometimes we get to play with fire. Well at least Chris Lee does. This flaming pumpkin is enough to keep them pesky kids from toilet-papering your house, or catching it on fire after they do.

The pumpkin is triggered by an Android phone, talking to a RFU-328 radio and Arduino. The Arduino triggers 2 relays, 1 to activate a furnace igniter, the other activates a solenoid that releases the flow of gas. The spray mechanism comes from an AirWick room spray and is filled with butane.

Chris made a comment about maybe converting this to shoot silly string out during actual Halloween, either way it’s a cool project.

With the advance of affordable 3D Printers, the home brew R/C vehicle community is booming with people making and designing their own parts. However, making your own RF controller is a different story.

Armed with a pair of Arduinos and nRF24L01 modules, Mujahed has a good start on one. On the transmitter side he’s reading a joystick module with an Arduino Uno and transmitting with one of the nRF24L01 modules. On the receiver side is another wireless module feeding an Arduino nano that is tied to a few servos. Everything on the car side is running off of a standard r/c car style 1800mAH battery.

The Electric Imp is a WIFI module with a brain. In some use cases it’s used to help connect your device to the cloud, as one of those ‘internet of things’. On other cases (like this one), it is the thing. Marcus has a cool little project that takes temperature readings and pushes them to the cloud.

Since the Imp is pretty power savvy, Marcus was able to power the project using a solar panel and charger. From there it uses a TMP36 analog temperature module to pull readings from. The temperature is read using the ADC and turned into an actual temperature number. The imp handles the rest by using the ThingSpeak api, which then collects and graphs the data.

In today’s somewhat creepy too-good-to-be-true technology announcement is this technique called Ambient Backscatter. In the demo, researchers create 2 devices that neither one takes batteries, yet they are able to communicate to each other. The devices harness radio waves that are already in the air like TV signals.

By either choosing to absorb or reflect the existing signals, the other device notices either a 1 or a 0. Thus data transfer wirelessly, without batteries! These devices have to run on real low power to work, because it’s consuming some of the rf signals to harness as power. The future for these devices is huge, imagine tons of little smart objects that can communicate, that don’t need batteries! People are already making small things that sip battery power but they do eventually need batteries. And typically those devices if they communicate wirelessly they are power hungry.

Amazing technology. Read more on the writeup on phys.org for a more detailed explanation, or watch the video below.

The guys over at SDR for Mariners put together a nice writeup on reducing the electrical interference on the good ol’ cheap RTL-SDR dongle. When the signal you’re looking for is very faint, you need to remove all of unwanted noise or else your signal gets difficult to separate. In their case the unwanted signal is in the form of FM radio.

Even if you aren’t a big RF nerd you know some of these remedies already like ferrite beads (you know those giant blocks on the ends of the expensive cables!). But I’m actually surprised at some of the other ones. I would have thought that the metal connector around a USB cable would help prevent noise, but according to their tests it was acting like a collector for their intrusive FM signal. By removing the shield and just connecting the data pins they dropped the noise by 10db. Not using the extension cable and just plugging straight in is even better.

So the winning combo appears to be all of their methods tested. A stick wrapped in aluminum foil, touching the metal of the USB plug, connected by a USB extension cable, inside a metal housing.

I’d love to see a picture of the final setup. Good tips to know when chasing down a faint signal.

This build uses good old FSK (frequency shift keyring) technology sending 1′s and 0′s through the air. Although its applied using infra-red, the same concept is used for RF. Also Infra-red is still technically wireless (lol). So on to the build. Just in-case you want to brush up on your FSK I recommend just straight up hitting wikipedia. (If not, here’s the TLDR version; A steady pulse is used to represent a 1, and a variation in the pulse width is used to represent a 0)

On the transmitter side a 555 timer is set up as a Astable Multivibrator, the digital input (fed from say a microcontroller) pulls down the transistor which modifies the frequency of the 555 timer, causing a 0. Leaving the pin high (representing a 1) leaves the 555 timer alone. The data is transmitted via infra-red led.

On the receiver side, a 565 PLL (Phase Lock Loop) IC locks on to the frequency of the 555 timer and outputs a 1 or a 0 when the signal alternates between the 2 frequencies.

This is a great project but mostly as an educational one. Full post up on gadgetronicx.

Peter got an idea to turn his Raspberry Pi into an WIFI access point in order to sniff out the traffic for research purposes. So after following some tutorials on Adafruit to get his Pi in AP mode he started dumping traffic.

He’s using hostapd for authentication, and started out just using good ol’ tcpdump to dump the traffic. After noticing the traffic was a little hard to follow from tcpdump he moved into running a man in the middle proxy script which allows him to see the traffic in a little more sane manor.

In his example he is spying on the traffic an app on his phone generates, but this method could be useful similar applications.

He has a bash script with his firewall rules up on his site, as well as some explanation of his test app on his site.